Historically, prospecting for precious metals has been a laborious pursuit for income. In recent times, prospecting has evolved into a venture typically undertaken by two different sorts: industrial operators and enthusiastic hobbyists. The mining industry, and the gold-mining industry in particular, has developed high technology-driven methods of location and extraction to leverage economies of scale and massive budgets. Hard-rock mining of lode deposits produces a large amount of the world's commercial gold and occurs in open-pit or underground mines using explosives to release rock embedded with gold. The rocks are crushed into a slurry, and a chemical leaching and electrowinning process purifies the gold.
Hobbyists, on the other hand, do not have the financial resources to take on large-sized installation prospecting work, and so typically will instead rove from site to site exploring for precious metals. Due largely to financial and portability considerations, hobbyists use tools and methods very similar to those first used in prospecting, and the manual labor associated with the effort has diminished little. Because most of the tools prospectors use have not changed greatly, the process of searching, classifying, and panning for precious metals is still a difficult task involving a great deal of digging, heavy lifting, stooping and bending over, and shaking dirt. Additionally, modern prospecting tools still require that the prospector first classify “raw” material and then filter gravel and debris from the fine materials before panning the fine material.
Modern prospectors often use metal detectors to help locate gold deposits. Once a site has been located, the prospector will prepare the site with equipment such as a shovel, a classification screen, and a gold pan. The prospector begins by digging up raw material such as dirt and gravel from the site, placing it on top of the classification screen, and shaking the screen, which filters the smaller rocks from the larger rocks. Three to four shovel-fulls of dirt can be classified at once, depending on the size of the classification screen. The larger rocks are discarded, and the remaining loose material and gravel can be panned. Material is placed into a pan. The prospector fills the pan with water or dips it into a river, and shakes, vibrates, or gyrates the pan to slosh water about inside the pan. At most pressures and temperatures, water is typically 1 gram per per cubic centimeter in density, rocks and gravel vary between 2 to 3 grams per cubic centimeter, and gold is 19.3 grams per cubic centimeter, and so this process allows the denser gold to settle to the bottom of the pan and the lighter materials to move to the top where they can be skimmed off and removed. Repeated shaking and skimming eventually leaves the dense materials at the bottom. If gold was in the pan initially, the gold will have settled near the bottom of the pan after this process has been repeated many times.
While panning is an effective means of filtering dense material from less dense, it can only be used to process a limited amount of fine material at once. Some prospectors use a sluice box to process a large amount of raw material. With a sluice box, a prospector can dump one shovelful of raw material after another into the upstream end of the sluice box, and riffles, or baffles along the bottom of the sluice box, trap gold as the water and raw material flow by. However, the classification step is still necessary when using a sluice box, as larger rocks will not be carried through the sluice box, but will instead come to rest on top of it, creating turbulence and vortices that can lessen the effectiveness of the sluice box at trapping fine gold. These processes are time-consuming because each requires several steps to reduce the raw material to pannable fine material, and thus little volume of raw material can be processed quickly.